Endometriosis model.

A: Sequence of the in vivo experiments. Endometriosis was induced on day 0 by transplantation of uterine tissue fragments from GFP+ donor animals into the peritoneal cavity of GFP- recipient mice. After 21 days, the take rate and size of newly formed endometriotic lesions were assessed and the lesions were analyzed by histology. For the analysis of the gut microbiota, fecal samples were collected 3 days before the transplantation of uterine tissue fragments as well as on day 7 and 21 after the induction of endometriosis. B: Macroscopic appearance of a well vascularized endometriotic lesion (borders marked by dotted line) at the abdominal wall of a C57BL/6 mouse on day 21. Scale bar = 650 μm. C: Fluorescence microscopy of a newly formed endometriotic lesion in the mesentery on day 21. Due to its bright GFP signal, the lesion (borders marked with dotted line) can be easily detected in blue light epi-illumination microscopy within the surrounding GFP- host tissue. Scale bar = 470 μm. D-F: HE-stained sections of endometriotic lesions at the abdominal wall (D, E) and the gut wall (F, G). Higher magnification (E, G = inserts in D, F) reveals a typical histomorphology of the lesions, i.e. cyst-like dilated glands with an epithelial layer (arrowheads), which are surrounded by a well vascularized endometrial stroma. Scale bars: D, F = 290 μm; E, G = 45 μm.